This invention relates to light reflective structures, and more specifically relates to a novel reflective structure for an elongated high intensity lamp which produces a more uniform light distribution across the width of an elongated parabolic reflector having the elongated lamp at or adjacent to its focus.
Lamps which may be infrared, ultraviolet, or the like are known for exposure of light-sensitive materials. Parabolic reflectors are also well known for use in connection with such elongated line-type light sources used, for example, for the exposure of photographic plates. When the elongated light source is placed at the focal point of the parabolic shape, the configuration achieves only partial success in obtaining an even and uniform light distribution across the width of the parabolic reflector. The parabolic reflector will tend to reinforce or produce an increased light intensity on the surface of the area directly in line with or directly beneath the light source. Areas which are laterally removed from the center of the reflector and from the light source region receive less direct light and less reflected light. As a result, there is an uneven distribution of light across the width of the area being illuminated, with the light intensity being highest toward the lateral center of the area beneath the reflector.
In accordance with the present invention, a novel reflector shape is provided which produces an improved light distribution across the area being illuminated by an elongated parabolic reflector which contains an elongated line-type light source at or near its focus. The more uniform light intensity applied to the material to be exposed may then allow use of lower intensity light sources or faster cycle times, or generally more accurate illumination of any flat area.
In carrying out the present invention, the light reflector is modified by having the central lateral region thereof inwardly deformed toward the line source. This will then cause the light previously reflected toward the center of the area being illuminated to be reflected generally away from the center, thereby to more uniformly distribute light across the lateral width of the reflector.
In deforming the parabola, the deformed region can take the form of a concave or inwardly bent surface; or can take the form of angularly inwardly bent sections which are each flat; or could take the form of a single flat section extending across the top of the reflector. In each case, the center of the reflector is deformed toward the light source and away from its normal parabolic configuration. The use of flat members in the deformed region is useful since they simplify the construction of the reflector by permitting the use of elongated flat reflector sheets.